Bioassay

A bioassay is an analytical method to determine concentration or potency of a substance by its effect on living cells or tissues.[1] Bioassays were used to estimate the potency of agents by observing their effects on living animals (in vivo) or tissues (in vitro).[2]

A bioassay experiment can either be qualitative or quantitative, direct or indirect.[3] If the measured response is binary, the assay is qualititative, if not, it is quantitative.[3]

Bioassay is used to detect biological hazards or give a quality assessment of a mixture.[4] Bioassay is often used to monitor water quality and also sewage discharge and its impact on surrounding [2]. It is also used to assess the environmental impact and safety of new technologies and facilities.[2]

Bioassay is a biochemical test to estimate the relative potency of a sample compound to a standard compound.[3][1] Typical bioassay involves a stimulus (ex. drugs) applied to a subject (ex. animals, tissues, plants) and a response (ex. death) of the subject is triggered and measured.[5] The intensity of stimulus is varied by doses and depending on this intensity of stimulus, a change/response will be followed by a subject.[5].

The first uses of bioassay dates back to as early as the late 19th century, when the foundation of bioassays was laid down by a German physician, Paul Ehrlich.[6] He introduced the concept of standardization by the reactions of living matter.[6][5] His bioassay on diphtheria antitoxin was the first bioassay to receive recognition.[7] His use of bioassay was able to discover that administration of gradually increasing dose of diphteria in animals stimulated production of antiserum.[8]

Many of the early bioassays consisted of using animals to test carcinogenicity of chemicals.[9] One well known example is a "canary in the coal mine" experiment.[10] To test for methane, miners would take methane-sensitive canaries to coal mines to ensure safe air. In 1915, Yamaigiwa Katsusaburo and Koichi Ichikawa tested the carcinogenicity of coal tar using inner surface of rabbit's ears.[9]

Through 1940s and 1960s, animal bioassay was primarily used to test for toxicity and safety of drugs, food additives and pesticides.[9]

In late 1960s and 1970s, reliance on bioassay increased as the public concern for occupational and environmental hazards increased.[9] While before this health risks of certain chemicals such as pesticide was tested in animal bioassay, it was still rare and testing was not seen often.[9]